Elimination of chromatin from somatic nuclei which is retained in the germ line occurs in numerous species including plants, animals and protozoa. The complexity of the germ line micronucleus in the ciliate protozoan Tetrahymena is about 10% higher than that of macronucleus which is transcriptionally active in the vegetative cell. I will investigate the phenomenon of chromatin elimination using Tetrahymena as a model system. The proposed study has three main objectives. First, we will use molecular cloning to isolate and characterize germ line specific DNA sequences. Second, the distribution of these sequences on the Tetrahymena chromosomes will be determined by Southern hybridization to whole genome restriction digests of micronuclear DNA from nullisomic strains of Tetrahymena. Third, we will determine whether germ line specific DNA sequences are transcriptionally active by using DNA clones to probe for complementary RNA sequences amid the transcriptional products from conjugating cells. This work will add to our relatively limited knowledge regarding the structure and function of germ line specific DNA sequences.